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## **Description**

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also include relevant motivation and context. Have in mind the following
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2. What is the improvement/solution?
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Adds QuickNode Failover for Monad. This needs a migration as Monad is
already in prod.

## **Changelog**

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CHANGELOG entry: added QuickNode fallback RPC for Monad.

## **Related issues**

Fixes:

## **Manual testing steps**

```gherkin
Feature: my feature name

  Scenario: user [verb for user action]
    Given [describe expected initial app state]

    When user [verb for user action]
    Then [describe expected outcome]
```

## **Screenshots/Recordings**

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### **Before**

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### **After**

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## **Pre-merge author checklist**

- [x] I’ve followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Adds migration to set QuickNode failover URLs for Monad, refactors SEI
migration to a shared util, updates configs, and expands tests.
> 
> - **Migrations**:
> - **109 (Monad)**: Adds `failoverUrls` to
`NetworkController.networkConfigurationsByChainId['0x8f']` RPC endpoints
using `process.env.QUICKNODE_MONAD_URL`.
>   - **107 (SEI)**: Refactored to use shared helper.
>   - Registered `109` in `migrationList` and async pipeline.
> - **Migration Utility**:
> - New `addFailoverUrlToNetworkConfiguration(state, chainId, version,
name, envVar)` with validation and Sentry error handling; reused by
107/109.
> - **Networks config**:
> - Added `'monad-mainnet'` QuickNode mapping and enabled failover URLs
for Monad in `PopularList`.
> - **Tests**:
> - New `109.test.ts` covering happy path, invalid states, and env-var
behavior.
> - Updated `107.test.ts` to spy `ensureValidState` and align
expectations.
>   - Extended `util/index.test.ts` for the new helper.
> - Added `QUICKNODE_MONAD_URL` to network-controller utils test env
setup.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
7388fc9. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->